1. Field of Invention
The present invention relates to an image processing apparatus for correcting image data, and in particular, to a technique for enhancing definition of image data.
2. Description of the Related Art
Image sensors of digital cameras, which have become prevalent in recent years, are provided with an increasingly larger number of pixels to enhance image quality, and become reduced in size to enhance portability. To provide such downsized image sensors with more pixels, some progress has been made on reduction in size of each pixel of digital image sensors.
However, on an imaging plane of a camera including an image sensor, incident light is diffracted and thus causes diffraction blur, which leads to a problem, wherein making each pixel of the image sensor smaller than the size of the diffraction blur does not enhance resolution (diffraction limit). Specifically, the diffraction blur has more influence when the lens of the imaging optical system is stopped down.
Conventional imaging apparatuses for curbing such influence given by the diffraction blur are described in Patent literature 1 and Patent literature 2.
The imaging apparatus in Patent literature 1 decreases a gain of its image sensor, instead of stopping down the lens of the imaging optical system, upon capturing an image of an object when an amount of light from the object is large. By doing so, signal outputs from the image sensor will not be excess, which prevents generation of the diffraction blur that is caused by stopping down the lens.
The imaging apparatus in Patent literature 2 uses, instead of stopping down the lens of the imaging optical system, a neutral density (ND) filter to control an amount of incident light, so as to reduce the incident light when the amount of light is large upon capturing an image. Such use of the ND filter prevents generation of the diffraction blur that is caused by stopping down the lens.